This invention relates to improved aqueous slurry explosives and to a method for their preparation. More particularly, the invention relates to thickened aqueous slurry explosives of the type comprising an inorganic oxidizing salt, an organic or inorganic fuel, water, and a thickening agent.
Aqueous slurry explosives are well known and have been widely accepted by users of commercial explosives. Such explosives generally contain a wide variety of ingredients. For instance, a slurry usually contains an inorganic oxidizing salt such as ammonium nitrate or an alkali or alkaline earth metal nitrate, e.g. sodium nitrate, or corresponding perchlorate salts or mixtures thereof. Organic and inorganic fuels are also often incorporated into such slurries. Organic fuels suitable for explosive slurries include a large variety of finely divided non-explosive carbonaceous materials such as carbon black, ground coal, fuel oils, vegetable oils, wax, wood pulp, vegetable pulp, sugar, nut meal, bagasse, etc. Inorganic fuels include finely divided metals and metal alloys such as aluminum, magnesium, and alloys thereof. Explosive slurries may optionally contain explosive sensitizers, depending upon the type of blasting agent desired. If a sensitizer is desired, such self-explosive materials as nitrostarch, trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), nitrocellulose, cyclotrimethylene trinitramine (RDX) and mixtures thereof may advantageously be employed.
Aqueous explosive slurries are generally thickened or gelled. Thickening serves to prevent segregation of the ingredients, to prevent leaks from containers having small perforations, to inhibit evaporation of liquids and to provide a resilient product when filled into elastic casings. Heretofore, aqueous slurries have been thickened with materials such as water soluble polysaccharides, e.g. methylcellulose, natural starches and gums. Galactomannan gums, particularly guar gum, have been preferred for this purpose. Such gums cause slurries to gel if employed in sufficiently high concentrations and cross-linking agents, such as borate and chromate salts or compounds of antimony or bismuth, may be added to accelerate gel formation.
During the manufacture of aqueous explosive slurries, it is desirable to thicken the ingredients early in the mixing process to prevent segregation. It has been found, however, that if the slurry is mixed or extruded into a casing after it has become quite thick or gelled, it tends to become desensitized, thus not being subject to easy or reliable detonation. Accordingly, a need exists for a thickener for aqueous explosive slurries which allows such slurries to be mixed or packaged subsequent to thickening without resulting in desensitization of the slurry.